Information detecting device to perform a color conversion operation on image read by a reading sensor

ABSTRACT

An information detecting device detects information from a target. The information detecting device includes processing circuitry. The processing circuitry is configured to perform a first information acquisition operation of acquiring first information from a target criterion, a second information acquisition operation of acquiring second information from the target, and an information conversion operation of converting the second information acquired by the second information acquisition operation, into third information, with the first information acquired by the first information acquisition operation, the third information having a dimension different from respective dimensions of the first information and the second information; and perform control such that an information-acquisition condition in the first information acquisition operation is identical to an information-acquisition condition in the second information acquisition operation.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is based on and claims priority pursuant to 35U.S.C. § 119(a) to Japanese Patent Application No. 2018-087369, filed onApr. 27, 2018, in the Japan Patent Office, the entire disclosure ofwhich is hereby incorporated by reference herein.

BACKGROUND Technical Field

Aspects of the present disclosure relate to an information detectingdevice, a reading device, an image forming apparatus, an informationdetecting method, and a recording medium.

Related Art

In a production print (PP) field, there is an in-machine sensingtechnique of reading a printed image with a sensing mechanism (in-linesensor) provided in a machine, such as a printing machine, and feeding aresult of the reading back to a printing mechanism. In general, thein-line sensor includes a mechanism identical to the mechanism of animage reading device. An image read by the in-line sensor is convertedfrom information regarding a color space of RGB into informationregarding a different dimensional color space of CMYK, Lab, or Luv.Then, the color information is fed back to an adjustment function.

A light emitting diode (LED) is mainly adopted as a light source for thein-line sensor. It has been known in general that manufacturingvariation causes variation in chromaticity between LEDs. As a techniqueof absorbing influence based on the variation during color-spaceconversion, proposed is a technique of reading a color sample identicalin color to the luminescent color of a light source, estimating thechromaticity of the light source from a result of the reading, andselecting a color conversion formula.

However, there are variations in luminescent intensity (luminousintensity) between LEDs. Typically, for adjustment of luminescentintensity, light quantity is adjusted with increase or decrease of thedriving current of an LED. The change of the driving current in thismanner causes a variation different from an estimate in the chromaticityof the LED. Color conversion performed with a color conversion formulagenerated on the basis of reading of a target criterion, such as a colorsample, causes deterioration in the accuracy of color conversion. Inrecent years, because printing quality requires highly colorreproducibility and highly color stability, in particular, deteriorationin the accuracy of color conversion results in a disadvantage inprinting quality. The disadvantage is a widely common problem betweeninformation detection fields for information other than chromaticity.Due to generalization, a difference between respectiveinformation-acquisition conditions, such as driving current, in firstinformation and second information, causes deterioration in the accuracyof conversion into third information.

SUMMARY

In an aspect of the present disclosure, there is provided an informationdetecting device that detects information from a target. The informationdetecting device includes processing circuitry. The processing circuitryis configured to perform a first information acquisition operation ofacquiring first information from a target criterion, a secondinformation acquisition operation of acquiring second information fromthe target, and an information conversion operation of converting thesecond information acquired by the second information acquisitionoperation, into third information, with the first information acquiredby the first information acquisition operation, the third informationhaving a dimension different from respective dimensions of the firstinformation and the second information; and perform control such that aninformation-acquisition condition in the first information acquisitionoperation is identical to an information-acquisition condition in thesecond information acquisition operation.

In another aspect of the present disclosure, there is provided a readingdevice that includes a light source, a reading sensor, and processingcircuitry. The light source is configured to irradiate a subject withlight. The reading sensor is configured to receive the light from thesubject. The processing circuitry is configured to control a firstreading operation of reading a criterion subject, a second readingoperation of reading the subject, a color-conversion-formula generationoperation of generating a color conversion formula with first colorinformation acquired by the first reading operation, and a colorconversion operation of converting second color information acquired bythe second reading operation, into third color information, with thecolor conversion formula, the third color information having a colorspace different from respective color spaces of the first colorinformation and the second color information; and perform control suchthat an irradiation condition of the light source in the first readingoperation is identical to an irradiation condition of the light sourcein the second reading operation.

In still another aspect of the present disclosure, there is provided aninformation detecting method of detecting information from a target. Theinformation detecting method includes performing a first informationacquisition operation of acquiring first information from a targetcriterion; performing a second information acquisition operation ofacquiring second information from the target; performing an informationconversion operation of converting the second information acquired bythe second information acquisition operation, into third information,with the first information acquired by the first information acquisitionoperation, the third information having a dimension different fromrespective dimensions of the first information and the secondinformation; and performing control such that an information-acquisitioncondition in the first information acquisition operation is identical toan information-acquisition condition in the second informationacquisition operation.

In still yet another aspect of the present disclosure, there is provideda non-transitory recording medium storing a plurality of instructionswhich, when executed by one or more processors, cause the processors to:perform a first information acquisition operation of acquiring firstinformation from a target criterion; perform a second informationacquisition operation of acquiring second information from the target;perform an information conversion operation of converting the secondinformation acquired by the second information acquisition operation,into third information, with the first information acquired by the firstinformation acquisition operation, the third information having adimension different from respective dimensions of the first informationand the second information; and perform control such that aninformation-acquisition condition in the first information acquisitionoperation is identical to an information-acquisition condition in thesecond information acquisition operation.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages and features thereof can be readily obtained and understoodfrom the following detailed description with reference to theaccompanying drawings, wherein:

FIG. 1 is a diagram of an exemplary basic configuration of aninformation detecting device according to the present embodiment;

FIGS. 2A and 2B are each a flowchart of an exemplary control flow of acontroller;

FIG. 3 is a diagram of an exemplary configuration of a reading deviceaccording to a first embodiment;

FIGS. 4A and 4B are each a flowchart of an exemplary control flow of amain controller;

FIGS. 5A to 5F are explanatory graphs for effect due to fixation of thedriving current value of a light source;

FIG. 6 is a diagram of an exemplary configuration of a reading deviceaccording to a first modification;

FIGS. 7A and 7B are each a flowchart of an exemplary control flow of amain controller;

FIGS. 8A and 8B are each a graph of a variation in chromaticity withfixation of driving current in the configuration according to the firstmodification;

FIG. 9 is a flowchart of a control flow of a light-quantity adjustmentoperation of maximizing the light quantity of a light source;

FIG. 10 is a flowchart of a control flow of a light-quantity adjustmentoperation with an extended density handling range in color conversion;

FIG. 11 is a diagram of an exemplary configuration of a reading deviceaccording to a second modification;

FIGS. 12A and 12B are each a flowchart of an exemplary control flow of amain controller; and

FIG. 13 is a view of an exemplary configuration of a multifunctionperipheral according to a second embodiment.

The accompanying drawings are intended to depict embodiments of thepresent disclosure and should not be interpreted to limit the scopethereof. The accompanying drawings are not to be considered as drawn toscale unless explicitly noted.

DETAILED DESCRIPTION

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentdisclosure. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise.

In describing embodiments illustrated in the drawings, specificterminology is employed for the sake of clarity. However, the disclosureof this specification is not intended to be limited to the specificterminology so selected and it is to be understood that each specificelement includes all technical equivalents that have a similar function,operate in a similar manner, and achieve a similar result.

Embodiments

Embodiments of an information detecting device, a reading device, animage forming apparatus, an information detecting method, and a programwill be described in detail below with reference to the accompanyingdrawings. Note that the embodiments are just exemplary, and thus eachembodiment may be appropriately combined with another or may bemodified.

FIG. 1 is a diagram of an exemplary basic configuration of aninformation detecting device according to the present embodiment. FIG. 1illustrates the configuration of an exemplary information detectingdevice 1 including an acquisition unit 11, an information conversionunit 12, and a controller 13. Note that as long as the informationdetecting device 1 includes at least the controller 13 capable ofcontrolling the acquisition unit 11 and the information conversion unit12, the acquisition unit 11 and the information conversion unit 12 maybe provided outside.

The acquisition unit 11 acquires respective pieces of information from atarget criterion and a target that are each an information-acquisitiontarget. The information acquired from the target criterion (firstinformation) is used as criterion information for the informationacquired from the target (second information).

The information conversion unit 12 converts the second informationacquired from the target, into third information, on the basis of thefirst information acquired from the target criterion. For example, theinformation conversion unit 12 converts the second information into thethird information, with an information conversion formula based on thefirst information. Here, the information conversion formula is aconversion formula for conversion into the third information indicatedwith a dimension different from the dimension of the second information(or the first information). The different dimension corresponds to acoordinate system indicated with a parameter group different from theparameter group of the second information (or the first information).The different in dimension indicates, for example, a difference in colorspace between an “RGB” color system and an “L*a*b*” color system.

The controller 13 controls the control targets to perform a firstinformation acquisition operation, a second information acquisitionoperation, and an information conversion operation. During the firstinformation acquisition operation, the acquisition unit 11 acquires thefirst information from the target criterion. During the secondinformation acquisition operation, the acquisition unit 11 acquires thesecond information from the target. During the information conversionoperation, the information conversion unit 12 converts the secondinformation into the third information, on the basis of the firstinformation (e.g., the information conversion formula based on the firstinformation).

Furthermore, the controller 13 controls the control target such that theinformation-acquisition condition in the first information acquisitionoperation is identical to the information-acquisition condition in thesecond information acquisition operation. Specifically, the controller13 performs control such that the respective information-acquisitionconditions are identical when the acquisition unit 11 acquires theinformation from the target criterion and the information from thetarget. The controller 13 controls the information conversion unit 12 onthe basis of the information-acquisition conditions.

FIGS. 2A and 2B are each a flowchart of an exemplary control flow of thecontroller 13. FIG. 2A illustrates a control flow at aninformation-detection preliminary stage including the first informationacquisition operation and the information conversion operation. FIG. 2Billustrates a control flow at an information-detection execution stageincluding the second information acquisition operation and theinformation conversion operation.

First, the controller 13 generates an information conversion formulawith the control illustrated in FIG. 2A at the information-detectionpreliminary stage. Specifically, as the first information acquisitionoperation, the controller 13 fixes the information-acquisition conditionof the acquisition unit 11 (S1), and causes the acquisition unit 11 withthe fixed information-acquisition condition, to acquire the firstinformation (S2).

Subsequently, as the information conversion operation, the controller 13causes the information conversion unit 12 to calculate the informationconversion formula, on the basis of the first information (S3). Theinformation conversion unit 12 retains the information conversionformula generated by the calculation.

In this manner, the controller 13 performs the first informationacquisition operation and the information conversion operation at theinformation-detection preliminary stage, to generate the informationconversion formula with the first information acquired from the targetcriterion.

Subsequently, the controller 13 performs information detection with thecontrol illustrated in FIG. 2B at the information-detection executionstage. Specifically, as the second information acquisition operation,the controller 13 causes the acquisition unit 11 with a conditionidentical to the information-acquisition condition at step S1, toacquire the second information (S5).

Subsequently, as the information conversion operation, the controller 13specifies the information conversion formula generated at step S3 andcauses the information conversion unit 12 to convert the secondinformation into the third information (S6).

With this configuration, the information detecting device according tothe present embodiment acquires the second information with aninformation acquisition condition identical to theinformation-acquisition condition at the acquisition of the firstinformation, and converts the second information into the thirdinformation, on the basis of the first information. That is theinformation detecting device according to the present embodiment fixesthe respective information-acquisition conditions at the same value inthe first information acquisition operation and the second informationacquisition operation, resulting in enhancement of the correlationbetween the first information and the second information. Thus, theinformation detecting device according to the present embodimentinhibits the accuracy of conversion into the third information fromdeteriorating due to the difference between the respectiveinformation-acquisition conditions of the first information and thesecond information, resulting in retention or improvement of theaccuracy of conversion into the third information.

Note that the information-acquisition conditions are preferably inagreement in terms of all factors related to the acquisition of theinformation (e.g., ambient temperature, and the driving current and thedriving voltage of the acquisition unit 11). However, even in a casewhere the information acquisition conditions are in agreement in termsof part of the factors, such as the driving current or the drivingvoltage of the acquisition unit 11, the accuracy of conversion into thethird information is inhibited from deteriorating, resulting inretention or improvement of the accuracy of conversion into the thirdinformation.

First Embodiment

Next, application of the information detecting device 1 illustrated inFIG. 1 to a reading device, will be described. For example, theinformation detecting device 1 is considered to be applied to a readingdevice (in-line sensor) used for calibration of a printing machine. As afirst embodiment, exemplary application to a reading device (in-linesensor) used for calibration of a printing machine, will be describedbelow.

FIG. 3 is a diagram of an exemplary configuration of the reading deviceaccording to the first embodiment. FIG. 3 illustrates the mainconfiguration of the reading device. A reading device 2 illustrated inFIG. 3 mainly includes a light source 21, an image sensor 22, a signalprocessing unit 23, a color conversion unit 24, acolor-conversion-formula setting unit 25, a light-source drive fixationcontroller 26, and a main controller 27. Note that FIG. 3 illustrates,as an exemplary configuration in which the reading device 2 is attachedto a printing machine, an image processing unit 28 provided at theprinting machine. The image processing unit 28 may be provided at theprinting machine as illustrated in FIG. 3, or may be provided at thereading device 2.

The light source 21 illuminates a reading target with light. Here,exemplary use of a pseudo-white LED as the light source 21, is given.The pseudo-white LED including a blue LED chip and a yellow phosphor(complementary color for blue), generates pseudo-white light withmixture of blue light emitted from the blue LED chip and yellow lightemitted from the phosphor excited by the blue light. For example, thephosphor includes transmissive resin containing yellow fluorescentmaterial. Note that the configuration of the pseudo-white LED describedhere is exemplary, and thus the pseudo-white LED may have a differentconfiguration. For example, an appropriate combination of an LED and aphosphor in different colors may be used. Unless otherwise specified, a“white LED” corresponds to a “pseudo-white LED”, below.

A “reading target (subject)” corresponds to a “target criterion” or a“target”. A “criterion chart (criterion subject)” and a “printed image(printing image)” in the “reading target” correspond to the “targetcriterion” and the “target”, respectively.

The image sensor 22 that is an exemplary “reading sensor”, includes acharge coupled device (CCD) or a complementary metal oxide semiconductor(CMOS). The image sensor 22 having a light receiving face, receivesreflected light from the reading target irradiated with the light by thelight source 21, on the light receiving face through an optical system(e.g., an optical lens and an optical mirror). The image sensor 22photoelectrically converts an optical image of the reading targetreceived on the light-receiving face, in units of pixels, and performs,for example, black-level correction to an image signal of the readingtarget. Then, the image sensor 22 outputs the image signal to thesubsequent stage. Note that FIG. 3 illustrates that the image sensoroutputs an image signal of an RGB image of red (R) color, green (G)color, and blue (B) color, exemplarily.

The signal processing unit 23 performs various types of signalprocessing, such as A/D conversion and shading correction, to the imagesignal output from the image sensor 22 (an R image signal, a G imagesignal, and a B image signal).

The color conversion unit 24 converts image data output from the signalprocessing unit 23, into an arbitrary color space value. FIG. 3illustrates that the color space value is converted from an “RGB” colorsystem into an “L*a*b*” color system, exemplarily. Here, a color spaceindicated in the “RGB” color system corresponds to a “first colorspace”, and a color space indicated in the “L*a*b*” color systemconverted by the color conversion unit 24 corresponds to a “second colorspace”. The color conversion unit 24 retaining color conversion formulaegenerated before factory shipment, for example, in a memory, convertsthe color space value from the first color space into the second colorspace with a color conversion formula from the color conversionformulae, to convert first information (or second information) intothird information.

For each driving current value for the light source 21, fixed by thelight-source drive fixation controller 26 at a setting stage(corresponding to the information-detection preliminary stage) beforethe factory shipment, the color-conversion-formula setting unit 25 setsthe corresponding color conversion formulae to the driving currentvalue, to the color conversion unit 24. At an utilization stage(corresponding to the information-detection execution stage) by a userafter the factory shipment, the color-conversion-formula setting unit 25estimates chromaticity with an output value (e.g., a “b*” value) of thecolor conversion unit 24 acquired by reading of the “criterion chart”.The color-conversion-formula setting unit 25 selects and determines, asa color conversion formula to be used in the reading device, an optimumcolor conversion formula close to the estimated chromaticity, from thecolor conversion formulae set in the color conversion unit 24.

The light-source drive fixation controller 26 fixes a driving currentvalue for the irradiation condition of the light source 21, and outputsthe fixed driving current value to the color-conversion-formula settingunit 25 for synchronization of the driving current value with colorconversion.

The main controller 27 controls the operation of the entire readingdevice 2. The main controller 27 issues a printing instruction to animage forming unit at the subsequent stage.

The image processing unit 28 converts the signal converted into thesecond color space (third information), into the printing format of theprinting machine (e.g., CMYK).

Here, the light source 21 and the image sensor 22 mainly correspond tothe acquisition unit 11 (refer to FIG. 1). The color conversion unit 24and the color-conversion-formula setting unit 25 mainly correspond tothe information conversion unit 12 (refer to FIG. 1). The light-sourcedrive fixation controller 26 and the main controller 27 mainlycorrespond to the controller 13 (refer to FIG. 1).

Next, a “first information acquisition operation”, a “second informationacquisition operation”, and an “information conversion operation” in thereading device 2 will be described.

FIGS. 4A and 4B are each a flowchart of an exemplary control flow of themain controller 27. FIG. 4A illustrates a control flow in which thefirst information acquisition operation and the information conversionoperation are performed at a color-detection preliminary stage. FIG. 4Billustrates a control flow in which the second information acquisitionoperation (or the first information acquisition operation) and theinformation conversion operation are performed at a color-detectionexecution stage.

First, the main controller 27 generates color conversion formulae withthe control illustrated in FIG. 4A, at the color-detection preliminarystage, for example, before the factory shipment. The main controller 27sets the generated color conversion formulae to the color conversionunit 24.

Specifically, the main controller 27 first performs light-quantityadjustment, and fixes a current value (S11). For the light-quantityadjustment, the driving current of the light source 21 is adjusted suchthat the irradiation state of the light source 21 meets a desired state.After the light-quantity adjustment, the light-source drive fixationcontroller 26 fixes the driving current at the adjusted value.

Subsequently, the main controller 27 causes the image forming unit atthe subsequent stage to print a criterion chart (S12), and causes theimage sensor 22 to read an image of the printed criterion chart (S13).

Subsequently, the main controller 27 calculates color conversionformulae, on the basis of image data of the criterion chart read by theimage sensor 22 (S14). The color-conversion-formula setting unit 25 setsthe calculated color conversion formulae to the memory of the colorconversion unit 24, and the memory retains the calculated colorconversion formulae.

Here, the calculated color conversion formulae each including, forexample, a higher-order conversion matrix including an arbitraryparameter group, are optimum to the adjusted driving current value. Notethat the color conversion formulae may be generated by a colorimeterfrom a printing image printed from the image data of the criterionchart.

Subsequently, the main controller 27 performs color detection with thecontrol illustrated in FIG. 4B, in use by the user after the factoryshipment (color-detection execution stage).

Specifically, in order to read a subject to which the color detection isto be performed, the main controller 27 first causes, for example, theimage forming unit to print an image (S21) and causes the image sensor22 to read the printing image (S22). The driving current of the lightsource 21 in the reading of the image is fixed at the driving currentvalue (adjusted value) fixed at the color-detection preliminary stage,by the light-source drive fixation controller 26.

Subsequently, the main controller 27 selects an optimum color conversionformula from the plurality of color conversion formulae, on the basis ofimage data of the printing image read by the image sensor 22 (S23).

Subsequently, the main controller 27 causes conversion of the colorspace value of the image data from the “RGB” color system into the“L*a*b*” color system, with the selected color conversion formula (S24).For example, the image processing unit 28 converts the converted colorspace value into CMYK, in accordance with an application at thesubsequent stage (S25). For example, the converted data is fed back tothe image forming unit at the subsequent stage, and is used forcorrection of the forming condition of the image forming unit.

Note that, according to the present embodiment, the example in which thedriving current is adjusted variably for the light-quantity adjustment,has been given. However, the light-quantity adjustment is not limited tothis, and thus may be made by voltage adjustment. The criterion chart isprinted by the image forming unit, but may be a medium of whichcoloration is known, such as a criterion colored board, the medium beingirrelevant to the image forming unit. Furthermore, the conversion of theimage processing unit 28 is not limited to CMYK, and thus may beappropriately changed in accordance with the application at thesubsequent stage.

In this manner, at the color-detection preliminary stage, the readingdevice 2 reads the image of the printed criterion chart while fixing thedriving current value of the light source 21, and generates the colorconversion formulae on the basis of the image data (corresponding to the“first information”). At the color-detection execution stage, thereading device 2 reads the printing image with the driving current valuefixed at the color-detection preliminary stage. With the colorconversion formula selected for the image data (corresponding to the“second information”), the reading device 2 converts the image dataindicated with the color space in the RGB color system (corresponding tothe “first color space”) into the image data (corresponding to the“third information”) indicated with the color space in the L*a*b* colorsystem (corresponding to the “second color space”).

Next, effect due to fixation of the driving current value of the lightsource 21 by the light-source drive fixation controller 26, will bedescribed.

FIGS. 5A to 5F are explanatory graphs for the effect due to fixation ofthe driving current value of the light source 21. FIGS. 5A and 5Billustrate the relationship in variation between the color conversionformulae and the chromaticity of the light source being used, under alimitative condition in consideration of no adjustment of the drivingcurrent of the light source. FIGS. 5C and 5D illustrate, in a case wherethe driving current of the light source requires adjusting, therelationship in variation between the color conversion formulae and thechromaticity of the light source being used, with no adjustment of thedriving current. FIGS. 5E and 5F illustrate, as in the reading deviceaccording to the present embodiment, in a case where the driving currentof the light source requires adjusting, the relationship in variationbetween the color conversion formulae and the chromaticity of the lightsource being used, with the driving current fixed. FIGS. 5A, 5C, and 5Eare each a graph of the relationship between the light wavelength andthe luminescent intensity of the light source 21 in the case. FIGS. 5B,5D, and 5F each illustrate the relationship in variation between thecolor conversion formulae and the chromaticity of the light source beingused in the case, on an XY chromaticity diagram.

First, the relationship in variation between the color conversionformulae and the chromaticity of the light source being used, will bedescribed with the case of FIGS. 5A and 5B. As illustrated in FIG. 5A,the luminescent intensity characteristic in the entire wavelength regionchanges in accordance with the mixing ratio of the blue light emittedfrom the blue LED and the yellow light of the phosphor. Mainly, theluminescent intensity characteristic of the light emitted from the blueLED is indicated in a blue region on the shorter-wavelength side.Mainly, the luminescent intensity characteristic of the light of thephosphor is indicated in a region longer in wavelength than the blueregion. The two regions include a peak in blue luminescent intensity anda peak in yellow luminescent intensity, respectively. The white LEDbeing used in the present embodiment has a manufacturing variation. Anexample of the manufacturing variation is ununiform coating in yellow ofthe phosphor. Thus, in accordance with the mixing ratio of blue andyellow in the white LED being used, the white LED has any ofcharacteristic graphs A to B.

FIG. 5B illustrates open circles (1, 2, 3, . . . ) in chromaticitycorresponding to the color conversion formulae (color conversion formula1, color conversion formula 2, color conversion formula 3, . . . ) setin the color conversion unit 24, and illustrates the chromaticity (x, y)of the white LED being used, with filled circles. As illustrated in FIG.5B, under the limitative condition in consideration of no adjustment ofthe driving current of the light source 21, the chromaticity changesmonotonously in accordance with the mixing ratio of the luminescentcolors. Thus, the chromaticity of the white LED being used (filledcircle) follows on a line of the chromaticity (open circles) (or in theneighborhood of the line). Thus, use of the color conversion formula ofthe chromaticity (open circle) closest to the chromaticity of the whiteLED being used (filled circle), enables inhibition of an error fromincreasing in color conversion.

Next, a variation in chromaticity in a case where the driving current ofthe light source 21 requires adjusting, will be described. Because thedriving current typically requires adjusting, this case requiresconsidering. FIG. 5C illustrates a change in the luminescent intensitycharacteristic in a blue region of the light source 21 in a case wherethe driving current of the light source 21 is adjusted forlight-quantity adjustment. FIG. 5C illustrates the adjustment from largecurrent to small current, exemplarily. As illustrated in FIG. 5C,increase of the driving current (to large current) causes the lightwavelength of the blue LED chip to shift to the longer wavelength side(A side of FIG. 5C). That is the luminescent wavelength in blue shifts.At this time, as in FIG. 5D, the change of the luminescent wavelength inblue causes the chromaticity of blue light (x, y) to change withparameter z different from parameters x and y. That is the chromaticitychanges irrelevantly to a monotonous change due to the mixing ratio ofthe luminescent colors. Thus, the chromaticity of the white LED beingused (filled circle) does not follow a line of the chromaticity (opencircles). Thus, in a case where, for example, the driving current of thewhite LED being used is adjusted to small current (B), the chromaticityof the white LED being used (filled circle) disagrees in correlationwith the chromaticity on the monotonous line (open circle). Even whenthe corresponding chromaticity (open circle 3 of FIG. 5D) is detectedfrom the previously prepared color conversion formulae on the monotonousline, the color conversion formula does not meet the chromaticity of thewhite LED being used (filled circle), resulting in a large error incolor conversion. Thus, the accuracy of color conversion deteriorates.

That is, in this case, the accuracy of color conversion deteriorates dueto the change of the driving current accompanied with the light-quantityadjustment. Thus, the optimization of the light quantity (S/N) isincompatible with the accuracy of color conversion.

As in the reading device according to the present embodiment, in a casewhere the driving current of the light source requires adjusting,fixation of the driving current enables the compatibility of theoptimization of the quantity of light with the accuracy of colorconversion.

Specifically, the color conversion formulae are generated while thedriving current of the white LED is fixed. Then, color detection isperformed with the fixed driving current. FIG. 5F illustrates amonotonous line of the color conversion formulae (chromaticity (opencircles)) in a case where the color conversion formulae are generatedwhile the driving current of the white LED is fixed at small current B,exemplarily. As illustrated in FIG. 5F, in a case where the drivingcurrent of the white LED being used is adjusted at the small current(B), there is the monotonous line corresponding to the chromaticity ofthe white LED. Thus, selection of a neighboring color conversion formulaon the monotonous line (corresponding line) enables inhibition of anerror in color conversion even in a case where the driving current isadjusted. Thus, the accuracy of color conversion can be inhibited fromdeteriorating. That is the optimization of the light quantity (S/N) iscompatible with the accuracy of color conversion.

As described above, uniformity of the driving current of the lightsource between generation of color conversion formulae and reading of atypical subject, enables offsetting of influence of a change inchromaticity due to the driving current, resulting in retention orimprovement of the accuracy of color conversion even in a case wherelight-quantity adjustment is performed. Therefore, the luminescentintensity of the light source can be optimized, and the accuracy ofcolor conversion can be prevented from deteriorating.

First Modification

According to the first embodiment, the plurality of color conversionformulae is set to the color conversion unit 24 at the color-detectionpreliminary stage, and an optimum color conversion formula is selectedfrom the plurality of color conversion formulae at the color-detectionexecution stage. According to a first modification, a color conversionformula is set to a color conversion unit 240 for an individual object(individual object, such as a white LED or a reading device), and colordetection is performed with the color conversion formula. Note that aconfiguration different from the configuration according to the firstembodiment, will be mainly described. The same elements between thefirst embodiment and the first modification are denoted with the samereference signs, and thus the descriptions of the same elements will beomitted.

FIG. 6 is a diagram of an exemplary configuration of a reading deviceaccording to the first modification. A reading device 2 according to thefirst modification illustrated in FIG. 6 is different in configurationfrom the reading device 2 according to the first embodiment (refer toFIG. 3) in that the plurality of color conversion formulae is limited toone individual object. As illustrated in FIG. 6, the color conversionunit 240 set with one color conversion formula, is provided.

FIGS. 7A and 7B are each a flowchart of an exemplary control flow of amain controller 27. FIG. 7A illustrates a control flow in which a firstinformation acquisition operation and an information conversionoperation are performed at a color-detection preliminary stage. FIG. 7Billustrates a control flow in which a second information acquisitionoperation (or the first information acquisition operation) and aninformation conversion operation are performed at a color-detectionexecution stage.

Steps S31 to S34 in FIG. 7A correspond to steps S11 to S14 in thecontrol flow indicated in the first embodiment (refer to FIG. 4A),respectively. A difference from the first embodiment is that an adjustedvalue for the individual object (current value A in this example) isused for fixation of a current value at step S31, instead of an adjustedarbitrary adjusted value. That is, basically, a color-conversiongeneration operation is required at least to be performed one time foran individual object. Note that, as long as a light source includes anLED as in the present configuration, in general, the lifetime of thelight source is long and a change in light quantity due to elapse issmall. Thus, even in a case where light-quantity adjustment is performedonly one time as in the present example, influence on the accuracy ofcolor conversion is small. Thus, a change in light quantity due toelapse is negligible.

Steps S41, S42, S43, and S44 in FIG. 7B correspond to steps S21, S22,S24, and S25 in the control flow indicated in the first embodiment(refer to FIG. 4B), respectively. A difference from the first embodimentis that the current value at step S42 is set at the adjusted value forthe individual object (current value A in this example) and step S23 isomitted because no color conversion formula requires selecting (refer toFIG. 4B).

FIGS. 8A and 8B are graphs of effect in a case where driving current isfixed with the configuration according to the first modification. Thepresent configuration causes generation of a color conversion formulafor an individual object while the driving current of the white LED isfixed. Then, color conversion is performed with the fixed drivingcurrent for the individual object. FIG. 8A illustrates a shift in theluminescent intensity characteristic in a case where the driving currentis changed, similarly to FIG. 5E.

FIG. 8B illustrates, for the white LED fixed at small current B, therelationship between the individual object and the chromaticity of thecolor conversion formula, exemplarily. FIG. 8B illustrates an opencircle as the chromaticity corresponding to the color conversion formulagenerated with the driving current of the white LED fixed at the smallcurrent (B). According to the present configuration, one colorconversion formula is provided for an individual object. Thus, FIG. 8Billustrates only one open circle, differently from FIG. 5F. According tothe present configuration, color conversion is performed with the whiteLED for which the color conversion formula is generated. Thus,performance of the color conversion with the fixed value (small currentB) at the generation of the color conversion formula, makes thechromaticity of the white LED and the chromaticity corresponding to thecolor conversion formula, in agreement. Thus, a filled circle overlapswith the open circle.

In this manner, the configuration according to the first modificationcauses, for an individual object of the light source, generation of acolor conversion formula with a driving current value meeting theindividual object. The color conversion formula can absorb an individualvariation in the chromaticity or the luminous intensity of the lightsource. Thus, there is no need to retain the plurality of colorconversion formulae in a memory, and the one color conversion formulameeting the individual object is required at least to be retained.Therefore, the present configuration enables cost reduction andminiaturization.

In a case where a color space is present between conversion formulae, amethod of selecting one arbitrary color conversion formula from finitecolor conversion formulae, theoretically causes an error in colorconversion. However, according to the present configuration, anoptimized color conversion formula generated for an individual object,is used in color conversion, resulting in further reduction of an errorin color conversion.

As described above, according to the present configuration, a colorconversion formula is generated for an individual object, so that anindividual difference can be absorbed. This arrangement theoreticallyenables inhibition of an error in color conversion, resulting inimprovement in the accuracy of color conversion.

Next, a light-quantity adjustment operation will be described. There arelarge variations in luminous intensity between LEDs, and thuslight-quantity adjustment is performed in general. First, alight-quantity adjustment operation of maximizing the light quantity ofthe light source, will described. Next, a light-quantity adjustmentoperation with an extended density handling range in color conversion,will be described.

FIG. 9 is a flowchart of a control flow of the light-quantity adjustmentoperation of maximizing the light quantity of the light source. First,the main controller 27 sets an initial light quantity (S111). Theinitial light quantity is set with the driving current at an arbitraryvalue. Here, in order to prevent an image sensor 22 from beingsaturated, the driving current is set such that a read value is lessthan a final-adjustment read value (target value B).

Subsequently, the main controller 27 reads a criterion medium, such as acriterion white board (S112), and determines whether the read value ofthe criterion medium has reached the target value B (S113).Specifically, the main controller 27 determines whether the read valuehas reached the target value B with the current light quantity.

In a case where determining that the read value has not reached thetarget value B (S113: No), the main controller 27 increases the drivingcurrent in order to further raise the light quantity (S114), reads thecriterion white board again (S112), and determines whether the readvalue has reached the target value B (S113). In this manner, repetitionof steps S112 to S114 causes the read value to converge to the targetvalue B.

As a result, in a case where determining that the read value has reachedthe target value B with the current light quantity (S113: Yes), the maincontroller 27 finishes the present light-quantity adjustment operation.

In this manner, performance of the light-quantity adjustment formaximization of the light quantity of the light source, enablesreduction of influence of photon shot noise, improvement of the S/N ofan image, and improvement of the accuracy of color conversion.

In the light-quantity adjustment operation illustrated in FIG. 9, thelight-quantity adjustment with the criterion white board is performedsuch that the read value of the criterion white board is not saturated.Thus, if a subject brighter in density than the criterion white board isread, theoretically, the read value of the subject is likely to besaturated, disabling color detection. That is a narrow density handlingrange in color conversion may be a disadvantage. In some cases, anapplication requires a density handling range rather than improvement ofS/N with a rise in light quantity. Thus, the density handling range isone of important factors for color detection.

FIG. 10 is a flowchart of a control flow of the light-quantityadjustment operation with the extended density handling range in colorconversion. Steps S121 to S124 illustrated in FIG. 10 correspond tosteps S111 to S114 illustrated in FIG. 9, respectively. The differencefrom FIG. 9 is that the target value B for determination of the readvalue is set at B*0.87 at step S123. That is, in order to read a subjectbrighter than the criterion white board, the adjustment target value forreading the criterion white board is previously set lower, so that thebrighter subject is handled. This example indicates the target value ina case where the density of the criterion white board is 0.06(conversion in reflectivity: approximately 87%). The target value islower by 13% than the target value in the light-quantity adjustment ofFIG. 9. That is a subject brighter by 13% than the criterion white boardcan be handled.

As described above, the adjustment target value for light-quantityadjustment, adjusted at a brighter level than the level of the criterionwhite board, extends the density handling range in color conversion, sothat the subject brighter than the criterion white board can be handled.

Note that, although the adjustment target value has a reduction of 13%in this example, the adjustment target value corresponds to 100% inreflectivity. That is further reduction of the adjustment target valuethan the value indicated in the example enables handling of areflectivity of 100% or more, namely, subjects in all density, inprinciple.

Second Modification

Reduction of influence of an error in quantization, enables enhancementof the accuracy of color conversion. A second modification describesreduction of influence of an error in quantization. Note that the sameelements between the first modification and the second modification aredenoted with the same reference signs, and thus the descriptions of thesame elements will be omitted. A configuration different from theconfiguration according to the first modification, will be mainlydescribed below.

FIG. 11 is a diagram of an exemplary configuration of a reading deviceaccording to the second modification. A reading device 2 according tothe second modification illustrated in FIG. 11 is different inconfiguration from the reading device according to the firstmodification (refer to FIG. 6) in that an amplifier 31 is provided.

The amplifier 31 amplifies an output of an image sensor 22, and outputsimage data after the amplification to a signal processing unit 23. Then,a color conversion unit 240 performs color detection with a colorconversion formula generated on the basis of the image data after theamplification.

FIGS. 12A and 12B are each a flowchart of an exemplary control flow of amain controller 27. FIG. 12A illustrates a control flow in which a firstinformation acquisition operation and an information conversionoperation are performed at a color-detection preliminary stage. FIG. 12Billustrates a control flow in which a second information acquisitionoperation (or the first information acquisition operation) and aninformation conversion operation are performed at a color-detectionexecution stage.

Steps S51, S53, S54, and S55 in FIG. 12A correspond to steps S31, S32,S33, and S34 in the control flow illustrated in the first modification(refer to FIG. 7A), respectively. The difference from the firstmodification is that the main controller 27 performsamplification-factor adjustment at step S52. After light-qualityadjustment, the main controller 27 performs the amplification-factoradjustment, and retains the amplification factor fixed at anamplification factor C.

Steps S61 to S64 in FIG. 12B correspond to steps S41 to S44 in thecontrol flow illustrated in the first modification (refer to FIG. 7B),respectively.

As described above, according to the second modification, the output ofthe image sensor 22 is amplified, and use of the image data after theamplification allows relative reduction of influence of an error inquantization. Therefore, the accuracy of color conversion can furtherimprove.

Second Embodiment

Exemplary application of the reading device 2 according to the firstembodiment to an image forming apparatus, will be described. Here,exemplary application of the reading device 2 to a multifunctionperipheral that is an exemplary image forming apparatus, will bedescribed.

FIG. 13 is a view of an exemplary configuration of the multifunctionperipheral according to a second embodiment. A multifunction peripheral100 illustrated in FIG. 13 includes an image reading unit (a readingunit 101 and an auto document feeder (ADF) 102) and an image formingunit 103 underlying the image reading unit. For description of theinternal configuration of the image forming unit 103, the internalconfiguration is illustrated with an external cover removed.

The ADF 102 automatically conveys an original mounted on a mount. Thereading unit 101 having an upper face including a contact glass on whichthe original is to be mounted, reads the original on the contact glass.Specifically, the reading unit 101 is a scanner internally including anilluminating device, an optical system, and an image sensor, such as acharge coupled device (CCD). The reading unit 101 causes the imagesensor to read reflected light from the original illuminated by theilluminating device, through the optical system.

The image forming unit 103 includes a sheet feeding roller 104 intowhich a recording sheet is to be manually fed and a recording-sheetsupply unit 107 that supplies a recording sheet. The recording-sheetsupply unit 107 has a mechanism of feeding a recording sheet from amultistage recording-sheet feed cassette. The supplied recording sheetis sent to a secondary transfer belt through a registration roller 108.

A toner image on a primary transfer belt is transferred, at a transferunit, to the recording sheet being conveyed on the secondary transferbelt.

The image forming unit 103 includes an optical writing device 109,tandem-system image forming devices 105 for, e.g., yellow (Y), magenta(M), cyan (C), and black (K), an intermediate transfer belt 113, and thesecond transfer belt. Through the image formation process of the imageformation devices 105, an image written by the optical writing device109 is formed as a toner image on the intermediate transfer belt 113.

Specifically, each of the image formation devices 105 including fourphotoconductor drums for, e.g., Y, M, C, and K rotatably, includes imageformation elements 106 including a charging roller, a developing device,a primary transfer roller, a cleaner unit, and a neutralizing device, onthe periphery of each photoconductor drum. The image formation elements106 function at each photoconductor drum, so that an image on thephotoconductor drum is transferred onto the intermediate transfer belt113 by the primary transfer roller.

The intermediate transfer belt 113 is stretched by a driving roller anda driven roller, the intermediate transfer belt 113 being disposedthrough the nip between each photoconductor drum and the correspondingprimary transfer roller. With the intermediate transfer belt 113traveling, a secondary transfer device secondary-transfers the tonerimage primary-transferred to the intermediate transfer belt 113, to therecording sheet on the secondary transfer belt. The recording sheet isconveyed to a fixing device 110 due to the traveling of the secondarytransfer belt. The fixing device 110 fixes the toner image as a colorimage onto the recording sheet. After that, the recording sheet isejected to an out-machine sheet ejection tray through a reading device114 (corresponding to the reading device 2). A criterion white board 115is disposed opposite the reading device 114. Note that, for double-sidedprinting, a reverse mechanism 111 reverses the recording sheet upsidedown, and then the reversed recording sheet is sent onto the secondarytransfer belt.

Because the image forming apparatus includes the reading device 2indicated in the first embodiment in this manner, the image formingapparatus having highly color reproducibility can be provided. Acriterion chart for generation of a color conversion formula is printedwith the color member of the image forming apparatus itself, and thecolor conversion formula is generated with the criterion chart. Thus,the color conversion formula can be optimized to the printingcharacteristic of the image forming apparatus itself, so that theaccuracy of color conversion can further improve.

There is a process of performing color inspection for a liquid crystaldisplay, sheet-metal coating, or highly color-rendering color member.The reading device 2 according to the first embodiment can be applied tothe process of the color inspection, in addition to the image formingapparatus. In that case, an inspection device having a highly inspectionfunction can be provided.

Third Embodiment

The information detecting device 1 illustrated in FIG. 1 can be appliedto, for example, a time-of-flight (TOF) ranging device. TOF is a rangingmethod of measuring the time of flight from when light is emitted to anarbitrary object until when the light returns, to measure the distance.For TOF, the time of flight of first light acquired for calibration froma criterion target is regarded as first information. The time of flightof second light acquired from a measurement target is regarded as secondinformation. Means of converting the time of flight into distanceinformation, with the time of light of first light, is regarded as aninformation converter. The distance information regarding themeasurement target is regarded as third information. The lightwavelength of the first light and the light wavelength of the secondlight are regarded as an information-acquisition condition. Means offixing the light wavelengths at the same wavelength is regarded as aninformation-acquisition controller. In this case, a difference in lightwavelength between the first light and the second light, causes theweight of the time of flight to change, resulting in an error inranging. However, the information detecting device 1 illustrated in FIG.1 makes the first light and the second light identical in lightwavelength, to enhance the correlation in the time of flight between thefirst light and the second light. Thus, the accuracy of conversion intodistance information can improve. That is the accuracy of ranging can beenhanced.

The controller of the information detecting device according to thepresent embodiment (the respective controllers according to theembodiments and the modifications are included) may include dedicatedhardware or a general-purpose computer. For the general-purposecomputer, a central processing unit (CPU) executes a program stored in,for example, a read only memory (ROM). Thus, the controller implementsthe functional units that perform the various operations, to control thevarious operations and each unit. The program previously installed onthe ROM may be provided. The program in an installable file format or inan executable file format, recorded on a computer-readable recordingmedium, such as a compact disc (CD)-ROM, a flexible disk (FD), aCD-recordable (R), or a digital versatile disk (DVD), may be provided.The program stored in a computer connected to a network, such as theInternet, may be downloaded for provision.

The above-described embodiments are illustrative and do not limit thepresent disclosure. Thus, numerous additional modifications andvariations are possible in light of the above teachings. For example,elements and/or features of different illustrative embodiments may becombined with each other and/or substituted for each other within thescope of the present disclosure.

Any one of the above-described operations may be performed in variousother ways, for example, in an order different from the one describedabove.

Each of the functions of the described embodiments may be implemented byone or more processing circuits or circuitry. Processing circuitryincludes a programmed processor, as a processor includes circuitry. Aprocessing circuit also includes devices such as an application specificintegrated circuit (ASIC), digital signal processor (DSP), fieldprogrammable gate array (FPGA), and conventional circuit componentsarranged to perform the recited functions.

The invention claimed is:
 1. An information detecting device to detectinformation from a target, the information detecting device comprising:processing circuitry configured to perform a first informationacquisition operation of acquiring first information from a targetcriterion irradiated with light from a light source, a secondinformation acquisition operation of acquiring second information fromthe target irradiated with light from the light source, and aninformation conversion operation of converting the second informationacquired by the second information acquisition operation, into thirdinformation, with the first information acquired by the firstinformation acquisition operation, wherein the third information has adimension different from respective dimensions of the first informationand the second information; and control the light source such that aninformation-acquisition condition used to drive the light source in thefirst information acquisition operation is identical to aninformation-acquisition condition used to drive the light source in thesecond information acquisition operation.
 2. A reading device,comprising: a light source configured to irradiate a subject with light;a reading sensor configured to receive the light from the subject; andprocessing circuitry configured to control a first reading operation ofreading a criterion subject, a second reading operation of reading thesubject, a color-conversion-formula generation operation of generating acolor conversion formula with first color information acquired by thefirst reading operation, and a color conversion operation of convertingsecond color information acquired by the second reading operation, intothird color information, with the color conversion formula, wherein thethird color information has a color space different from respectivecolor spaces of the first color information and the second colorinformation; and control the light source such that an irradiationcondition used to drive the light source in the first reading operationis identical to an irradiation condition used to drive the light sourcein the second reading operation.
 3. The reading device according toclaim 2, wherein the color-conversion-formula generation operation isperformed for an individual object of the light source.
 4. The readingdevice according to claim 2, wherein the light source includes a lightemitting diode.
 5. The reading device according to claim 2, wherein theirradiation condition used to drive the light source includes a value ofa driving current of the light source.
 6. The reading device accordingto claim 5, wherein the processing circuitry is configured to: perform alight-quantity adjustment operation of adjusting the value of thedriving current before the color-conversion-formula generationoperation; and perform adjustment in the light-quantity adjustmentoperation such that a light quantity of the light source is maximized.7. The reading device according to claim 5, wherein the processingcircuitry is configured to: perform a light-quantity adjustmentoperation of adjusting the value of the driving current before thecolor-conversion-formula generation operation; and perform adjustment inlight quantity in the light-quantity adjustment operation such that thefirst color information and the second color information are notsaturated even in a case where the subject brighter than the criterionsubject is read.
 8. The reading device according to claim 7, wherein thesubject read in the second reading operation is brighter than thecriterion subject read in the first reading operation.
 9. The readingdevice according to claim 5, further comprising an amplifier configuredto amplify a signal from the reading sensor, wherein an amplificationfactor of the amplifier is adjusted after a light-quantity adjustmentoperation and before the color-conversion-formula generation operation.10. An image forming apparatus comprising: the reading device accordingto claim 2; and an image forming device configured to form an image,based on the third color information converted by the reading device.11. The image forming apparatus according to claim 10, wherein thecriterion subject includes a printing image formed by the image formingdevice.
 12. The reading device of claim 2, wherein the processingcircuitry is further configured to control the light source such that afirst driving current used to drive the light source in the firstreading operation is identical to a second driving current used to drivethe light source in the second reading operation.
 13. The reading deviceof claim 2, wherein the processing circuitry is further configured tocontrol the light source such that a first driving voltage used to drivethe light source in the first reading operation is identical to a seconddriving voltage used to drive the light source in the second readingoperation.
 14. An information detecting method of detecting informationfrom a target, the information detecting method comprising: performing afirst information acquisition operation of acquiring first informationfrom a target criterion irradiated with light from a light source;performing a second information acquisition operation of acquiringsecond information from the target irradiated with light from the lightsource; performing an information conversion operation of converting thesecond information acquired by the second information acquisitionoperation, into third information, with the first information acquiredby the first information acquisition operation, wherein the thirdinformation has a dimension different from respective dimensions of thefirst information and the second information; and controlling the lightsource such that an information-acquisition condition used to drive thelight source in the first information acquisition operation is identicalto an information-acquisition condition used to drive the light sourcein the second information acquisition operation.